Ammo-ni′ac-al En′gine.
This motor seems to be yet in an inchoate state, but has received some attention in
Europe.
The machine described is the invention of
M. Froment.
The
London “Mechanics' magazine” thus refers to it (it appears to have been at work — or rather in action, for it was not usefully employed — at the
Paris Exposition): “Strong liquid ammonia is used in the boiler, and the vapor generated is said to be a mixture of at least eighty parts of ammoniacal gas and twenty parts of steam, so it may be fairly called an ammoniacal engine.
The principal recommendations of ammonia, when applied as a motive-power, consist in the small amount of fuel required, and the short time it takes to get up the steam, so to speak.
The economy in fuel is very considerable, being about one fourth of that required to generate steam alone.
As regards the boiler, it may be of either of the ordinary forms, the only complete novelty being the apparatus for condensing the steam and ammonia.
The gas disengaged (about six atmospheres at 110° Centigrade with an ordinary solution of ammonia) does its work in the cylinder and then escapes into the tubes of a condenser, where the steam is condensed and the gas is cooled.
The gas then meets with a cold liquid from an injector, which dissolves it, and the solution is carried on into a vessel called the ‘dissolver,’ from which it is pumped back into the boiler to do its work over again.
The liquid for the injector is taken from the boiler, and is cooled before meeting with the ammoniacal gas by passing through a worm surrounded with cold water.”
“Ammonia, at the temperature of our atmosphere, is a permanent gas of well-known pungent odor.
It is formed by the union of three volumes of hydrogen to one of nitrogen, condensed into two volumes.
Its density is 596; air being 1,000.
The density of the liquid, compared with water, is 76, or about one quarter lighter than that liquid.
Its vapor at 60° Fahr.
gives a pressure of 100 pounds to the square inch, while water, to give an equivalent pressure, must be heated to 325° Fahr.
The volume of ammoniacal gas under the above-named pressure is 983 times greater than the space occupied by its liquid, while steam, under identical pressure, occupies a space only 303 times greater than water.” —
Annals of Chemistry (
French).
Ammoniacal gas, which is an incidental and abundant product in certain manufactures, especially that of coal-gas, and which makes its appearance in the destructive distillation of all animal substances, is found in commerce chiefly in the form of the aqueous solution.
It is the most soluble in water of all known gases, being absorbed, at the temperature of freezing, to the extent of more than a thousand volumes of gas to one of water; and at the temperature of 50° Fahr., of more than eight hundred to one.
What is most remarkable in regard to this property is that, at low temperatures, the solution is sensibly instantaneous.
This may be strikingly illustrated by transferring a bell-glass filled with the gas to a vessel containing water, and managing the transfer so that the water may not come into contact with the gas until after the mouth of the bell is fully submerged.
The water will enter the bell with a violent rush, precisely as into a vacuum, and if the gas be quite free from mixture with any other gas insoluble in water, the bell will inevitably be broken.
The presence of a bubble of air may break the force of the shock and save the bell.
This gas cannot, of course, be collected over water.
In the experiment just described, the bell is filled by means of a pneumatic trough containing mercury.
It is transferred by passing beneath it a shallow vessel, which takes up not only the bellglass, but also a sufficient quantity of mercury to keep the gas imprisoned until the arrangements for the experiment are completed.
The extreme solubility of ammoniacal gas is, therefore, a property of which advantage may be taken for creating a vacuum, exactly as the same object is accomplished by the condensation of steam.
As, on the other hand, the pressure which it is capable of exerting at given temperatures is much higher than that which steam affords at the same temperatures; and as, conversely, this gas requires a temperature considerably lower to produce a given pressure than is required by steam, — it seems to possess a combination of properties favorable to the production of an economical motive-power.
Ammonia, like several other of the gases called permanent, may be liquefied by cold and pressure.
At a temperature of 38.5° C., it becomes liquid at the pressure of the atmosphere.
At the boilingpoint of water it requires more than sixty-one atmospheres of pressure to reduce it to liquefaction.
The same effect is produced at the freezing-point of water by a pressure of five atmospheres, at 21° C. (70° Fahr.) by a pressure of nine, and at 38° C. (100° Fahr.) by a pressure of fourteen.
—
Barnard.
Lamm's Ammonia Engine is driven by the expanding pressure of liquefied ammonia, and is specially adapted for small powers, especially portable engines for street cars, etc. The ammonia is to be liquefied at a central station, at which the reservoirs on the cars receive their supply.
The engine is driven by the force of the gas upon the piston, and the gas is exhausted into a body of water surrounding the gas reservoir.
The absorption of the gas by the water is instantaneous, and the water derives an increment therefrom which is imparted, through the walls, to the contents of the reservoir.
See “Engineering and mining journal,” Vol.
X. p. 65.
